/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.extensions.sql.impl.rule;



import com.bff.gaia.unified.sdk.extensions.sql.impl.rel.UnifiedLogicalConvention;

import com.bff.gaia.unified.sdk.extensions.sql.impl.rel.UnifiedUnnestRel;

import org.apache.calcite.plan.RelOptRule;

import org.apache.calcite.plan.RelOptRuleCall;

import org.apache.calcite.plan.volcano.RelSubset;

import org.apache.calcite.rel.RelNode;

import org.apache.calcite.rel.SingleRel;

import org.apache.calcite.rel.core.Correlate;

import org.apache.calcite.rel.core.Uncollect;

import org.apache.calcite.rel.logical.LogicalCorrelate;

import org.apache.calcite.rel.logical.LogicalProject;

import org.apache.calcite.rex.RexFieldAccess;

import org.apache.calcite.rex.RexNode;

import org.apache.calcite.sql.SemiJoinType;



/**

 * A {@code ConverterRule} to replace {@link Correlate} {@link Uncollect} with {@link

 * UnifiedUnnestRule}.

 */

public class UnifiedUnnestRule extends RelOptRule {

  public static final UnifiedUnnestRule INSTANCE = new UnifiedUnnestRule();



  // TODO: more general Correlate

  private UnifiedUnnestRule() {

    super(

        operand(

            LogicalCorrelate.class, operand(RelNode.class, any()), operand(SingleRel.class, any())),

        "UnifiedUnnestRule");

  }



  @Override

  public void onMatch(RelOptRuleCall call) {

    LogicalCorrelate correlate = call.rel(0);

    RelNode outer = call.rel(1);

    RelNode uncollect = call.rel(2);



    if (correlate.getCorrelationId().getId() != 0) {

      // Only one level of correlation nesting is supported

      return;

    }

    if (correlate.getRequiredColumns().cardinality() != 1) {

      // can only unnest a single column

      return;

    }

    if (correlate.getJoinType() != SemiJoinType.INNER) {

      return;

    }



    if (!(uncollect instanceof Uncollect)) {

      // Drop projection

      uncollect = ((SingleRel) uncollect).getInput();

      if (uncollect instanceof RelSubset) {

        uncollect = ((RelSubset) uncollect).getOriginal();

      }

      if (!(uncollect instanceof Uncollect)) {

        return;

      }

    }



    RelNode project = ((Uncollect) uncollect).getInput();

    if (project instanceof RelSubset) {

      project = ((RelSubset) project).getOriginal();

    }

    if (!(project instanceof LogicalProject)) {

      return;

    }



    if (((LogicalProject) project).getProjects().size() != 1) {

      // can only unnest a single column

      return;

    }



    RexNode exp = ((LogicalProject) project).getProjects().get(0);

    if (!(exp instanceof RexFieldAccess)) {

      return;

    }

    int fieldIndex = ((RexFieldAccess) exp).getField().getIndex();



    call.transformTo(

        new UnifiedUnnestRel(

            correlate.getCluster(),

            correlate.getTraitSet().replace(UnifiedLogicalConvention.INSTANCE),

            outer,

            call.rel(2).getRowType(),

            fieldIndex));

  }

}